QUOTE ABOUT THE importance of the witches in the whole play.

I can give you a couple:

Banquo warns Macbeth that “instruments of darkness” often tell half-truths “to win us to our harm” (1.3.125–126).\

This scene sets up the basis for the entire play. They are the "suggestions" or prophesies that spark Macbeth's obsession and paranoia,

First witch

All hail, Macbeth! Hail to thee, thane of Glamis!

Second Witch
All hail, Macbeth! Hail to thee, thane of Cawdor!

Third Witch
All hail, Macbeth, that shalt be king hereafter!

Ac1 sc 1